Low-Temperature Hydrous Pyrolysis (LTHP) on Oil-Field Core-Samples for Estimating Original In-Place Retained Oil in Mature Source Rocks and Tight-Oil Reservoirs
The amount of original‐oil‐in‐place (OOIP) is routinely estimated by conventional core analysis techniques and geochemical tests such as programmed non‐isothermal pyrolysis. A relatively new method is low‐temperature hydrous pyrolysis (LTHP) that was introduced by Lewan and Sonnenfeld (2017). As they described for mature Niobrara cores, LTHP releases retained oil that is similar to produced oil. Importantly, LTHP released oils are not controlled by volatilization conditions and minimize the inclusion of polar‐rich bitumen. LTHP is a technique in which crushed mature source‐rock core is isothermally heated in contact with liquid water at 300°C for 24 to 72 hours. These conditions, allow retained oil to be released from the mature rock by thermal expansion and water displacement of the oil and its dramatic difference in miscibility with polar‐rich bitumen in the presence of water, but are not sufficient to generate oil from the bitumen or kerogen within mature source rocks. Chesapeake Energy has been applying the LTHP method in their Reservoir Technology Center hydrous‐pyrolysis lab with favorable results. The method has also been extended to determine quality and quantities of retained oil in nonsource‐rock tight‐oil reservoirs. Quantities of released oil typically are sufficient to determine API gravity, gas chromatography, and gas chromatography/mass spectrometry signatures. Examples of LTHP within this presentation include a series of samples that illustrate the changes in quantity and quality of retained oil with increasing thermal maturity of a source rock. Additionally, released oils in mature source rocks and non‐source tight‐oil reservoirs, will be compared highlighting the important consideration of evaporative losses from cores. LTHP, which releases a true and collectable petroleum phase, is not intended to replace conventional core analyses or programmed pyrolysis, but rather supplement these better known, inexpensive and more rapid analyses.
AAPG Datapages/Search and Discovery Article #90349 © 2019 AAPG Hedberg Conference, The Evolution of Petroleum Systems Analysis: Changing of the Guard from Late Mature Experts to Peak Generating Staff, Houston, Texas, March 4-6, 2019